Electron ray voltage indicator



g- 1939- K. s. JACKSOL' 2,i?, 2

ELECTHOfi RAY VOLTAGE INDICATOR Filed May 27, 1938 s/ m/ o/h e' iabe 13009220190 'j #5 /o 5 0 mvrmz. GRID VOUAGE INVENTOR. KEENE 5. JA CKSON ATTORNEY.

Patented Aur-s: l, 1939 ELECTRON RAY VOLTAGE INDICATOR Keene S. Jackson, Springfield, N. 5., assignor, by mesne assignments, to Radio Corporation of America, New York, N. Y., a corporation of Delaware Application May 27, 1938, Serial No. 210,335

4 Claims. (Cl. 171-95) My invention relates to visual voltage or tuning indicators of the electron ray type, particularly to tuning indicators for radio receiving sets.

A tuning indicator for radio receivers now in of electrons and the size of the shadow angles 6 and 1, represented in Figures 2.

Means are provided according to my invention for reducing shadow angle 6 to zero when the commercial use comprises an electron discharge level of the received carrier wave is low and for 5 device with a cathode coaxial with a dish-shaped closing shadow angle 1 only when the strength of anode or electron target interiorly coated with the received carrier is high. The voltages applied fluorescent material which glows when bomto the ray-control electrodes are obtained rebarded by electrons. Parallel to the cathode and pee vely frOm a Single Source Of voltage in the in the electron-path between the cathode and radio receiver proportional to the strength of the 10 if target is an electron ray-controlling electrode received carrier. A common means for deriving connected to a voltage indicative of the resonant a direct current proportional to the strength of condition of the radio receiver. Usually the the received carrier, shown in Figure 1, comprises voltage applied to the ray-control electrode is a detector 8 in series with a load resistor 9 and 14 increased as the radio receiver is tuned to a the Secondary Winding of a transformer 0 15 carrier so that the electron shadow cast by the pled t0 the radio o e e e frequency ray-control electrode on the target closes or 0111195 0f the radio receiver- The v e gene reduces t a minimum and preferabl t ated across resistor 9 is applied, according to my 1 shadow angle is zero at resonance. Although invention, directly to the control grid H of a the voltage applied to the ray-control electrode Screen gridemplifier through filter resistor 20 may be taken from an automatic volume control T1115 ect current Yoltage if deslred circuit, the shadow angle, when adjusted to be applleii also to the gnds of amplifiers in the close on strong signals, will not completely close receiver through conductor for auto q to give accurate tuning indication on weak signals. matmauy controlling the gain in those ampnfiers- 5 The object of my invention is a visual tuning Anode l5 and screen grid i6 are connected to a 1 indicator which will accurately indicate resonance voltage Source through resistors and 7 I gialzg'radio receiver for both stron and weak si ipace fi: m pn i tiu il t am s an screen gr respective y oug res s ors 32 2: 33? fis'ggzi gg g g sg gfi gg gzi and I9 and produces voltage drops which lower 30 ticmamy in the appended claims but the invem the voltage of ray-control electrodes-4 and 5 with respect to the target. The amount of current t1on itself will best be understood by reference to n i thr h i t '8 9 d t i d b the following description taken in connection ow ng Dug ress or or mm M y With the accompanying drawing inwhich Figures control grid ll, determines the potential of r 35 l and 4 are diagrammatic representations of a anodes and I6 and the directly connected my- 85 j tunm indicat r t b d i b d control electrodesfi and 5. Accordingly, the bias g o u t C m l S em 0 my on control grid H, which is proportional to the t f Figure Is an end i of the vlsual carrier signal strength, controls the shadow indicator tube connected according to my invenangles 5 and-L 40 tion, and Figure 3 showscurves explanatory of The screen grid tube n is selected with a an .g

the operation of my improved tuning indicator. smeaned remote when m which the plate The electron W tube Shown Flgur? 1 and rent reduces to zero only with a high negative described in detail in the co-pending application control grid bum I have found that in tubes of Walter van B. Roberts Serial No. 1 98,717, filed the type commercially known as t 7 ma a March Q and afsslgned to Radlo COrPOmor 6D6., the plate current has a suiilciently low e I tron of America, comprises an envelope l enclosing value, when th control grid voltage 1 24 lt cathode 3 Coaxial with a dish-Shaped electron source I1 is 100 volts, and resistors l8 and to are target 2 interiorly sensitized with a material 200,000 ohms h, t t t had w angle 1 ap- 'f which glows when bombarded with electrons. preaches zero and that the shadow angle 6, con- Rod 01' fin-shaped ray-control electrodes 4 and 5 trolled by the screen grid current, approaches 50 supported on opposite sides and parallel to the zero at about -9 volts control grid bias. The cathode, are adapted to deflect the electrons fiowrelation of the control grid voltage at H and ing from the cathode to the target. The poten-- the plate current and the screen grid current, tial of ray-control electrodes 4 and 5 with rerepresented by shadow angles I and 6 respec- Spe t0 the Cathode e m nes t e deflect oii tively,have beenplottedin curves shown in Figure 55 are at a maximum when the control grid voltage.

is zero. As the control grid voltage is gradually increased in a negative direction, indicative of approach to resonance, the shadow angle 6 rapidly decreases and'becomes zero at 9 volts. At this voltage, however, shadow angle 1 has not appreciably changed and closes gradually and becomes zero only at about -24 volts.

In operation weak signals may be accurately tuned in by observing the closure angle at 6. Upon tuning in strong signals, shadow angle 6 becomes zero and the carrier may be accurately tuned in by observing shadow angle I. Good results have been obtained by adjusting the values of resistors 18 and I! to about 200,000 ohms each and the voltage of source I1 to 100 volts when applied to an amplifier of the 6K! type. The difference between the .control grid voltage at which the two shadow angles become zero may be adjusted by changing the ratio of resistance of resistors l8 and |8. If, for example, resistor I9 were increased in value the shadow angle 6 produced by ray-control electrode 5 would close at a higher-negative control grid voltage.

The tuning indicator embodying my invention, shown in Figure 4, comprises means for controlling the potentials of the two ray-control electrodes and for changing said potentials at diflercut rates in response to changes in the control grid voltage of the amplifier. In this embodiment of my invention resistor 20 is connected between the voltage source and the anode of a conventional amplifier 2|. The target is connected 5 to the high voltage end of the resistor and the my control electrodes are tapped tothe resistor at spaced points so that the shadow angles produced by ray-control electrodes 4 and 5 may be varied at different rates by thecontrol grid voltage of amplifier 2| as in Figure 1. For a given diflerence in the control grid voltage at which the two shadow angles close, the relative values of the two portions of resistor 20 may be readily determined. with the left and right hand portions of resistor 20 adjusted to 100,000 and 250,000 ohms each, the shadow angle of ray-control electrode 5 reduces to zero first with a negative grid bias voltage of 16.5 volts, and the shadow angle of ray-control electrode 4 reduces to zero with a 0 grid control bias of 27.5 volts where the amplinance in a radio receiver whether the level of the received carrier is high or low.

I claim: 1. A visual indicator of variable voltages comprising a cathode. an electron target with a surf face facing said cathode which fluoresces with electron bombardment, two ray-control electrodes on opposite sides 01 sa d. a h de f r casti g an areas-m electron shadow on said target, means for controlling the potential of one of said ray-control electrodes, means for controlling the potential of the other of said ray-control electrodes, said control means comprising an amplifier for changing said potentials at difierent rates in response to changes of said variable voltage comprising a cathode, control electrode, screen grid, and anode, said anode and screen grid being separately connected to said ray-control electrodes, resistors connected between said ray-control electrode and target, said control electrode being biased by said variable voltage.

2. A visual indicator of variable voltages comprising a cathode, a target facing said cathode which fiuoresces upon electron bombardment, two spaced ray-control electrodes between said cathode and target, means for changing the potentials of said ray-control electrodes with respect to said cathode and target in response to said variable voltages comprising an amplifier with a cathode, control grid, screen grid, and

anode, a voltage source connected at one end to the amplifier cathode and connected at the other end to said target and through resistors to said screen grid and anode, the two ray-control electrodes being connected to the resistors at points of different potentials.

3. A visual indicator of variable voltages comprising acathode. a target facing said cathode which fluoresces upon electron bombardment,

two spaced ray-control electrodes between said target and cathode, means for changing the potentials of said ray-control electrodes with respect to said cathode in response to said variable voltages comprising an amplifier with a cathode,

control grid, screen grid, and anode, a voltage source connected at one end to the amplifier cathode and connected at the other end through a resistor to said anode, said other end of the voltage source being connected to said screen" grid through a second resistoryone ray-control electrode being connected to said anode and the other ray-control electrode being connected to said screen grid, and means for impressing said variable voltages on said control grid.

4. A visual indicator of variable voltages comprising a cathode, a target facing said cathode which fiuore'sces upon electron bombardment, two spaced ray-control electrodes between said target and cathode, means for changing the potentials of said ray-control electrodes in response to said variable voltages comprising an amplifier with a cathode, control grid, screen grid and anode, a voltage source connected at one end to the amplifier cathode and connected at the other end to said target and through a resistor to said anode, the two ray-control electrodes being con- 'nected to spaced points on said resistor, and

means for irn'ressing said variable voltages on said control rid.

'KEENE S. JACKSON. 

